It would be GREAT, especially for agencies, to be able to re-use sections fom one site to another,
Or to be able to re-use classes. Or to create somewhere a bank of classes to re-use in all project. Things like that.
You can get your agency a Team/Organization plan. It comes with the possibility to build templates. So you elect some site as templates and members of your team can start a project with them.
I know it’s not exactly what you’re asking for but it’s worth mentioning